Folded membrane dialyzer

ABSTRACT

The present invention relates to an apparatus for the dialysis of two fluids and the method of making the same and is directed particularly to an apparatus for the dialysis of blood. The present invention uses a semipermeable membrane in sheet form, the membrane being folded into a large number of very closely spaced pleats. Support members are contained in all the pleats on one side of the membrane, all of the edges of which are sealingly embedded in a plastic material constituting at least a portion of the housing to give separate fluid chambers on the two sides of the membrane. A first fluid passes through the first such chamber within the pleats in a direction generally parallel to the creases of the pleats while a second fluid flows through the second chamber on the opposite side of the membrane pleats in a direction countercurrent to the first fluid. The apparatus is constructed either by placing the assembled folded membrane in a preconstructed rectangular casing and injecting a plastic material so as to surround and embed the edges of the membrane in the plastic material, or by placing the assembled folded membrane in a mold to form the housing by injecting a plastic material into the mold so as to surround and embed the edges of the membrane in the plastic material.

nite States arkley Primary Examiner-Frank A. Spear, Jr. Attorney, Agent,or FirmRoland A. Anderson; John A. Horan; Robert James Fisher [57]ABSTRACT The present invention relates to an apparatus for the [4 1 Jan.29, 197

dialysis of two fluids and the method of making the same and is directedparticularly to an apparatus for the dialysis of blood. The presentinvention uses a semipermeable membrane in sheet form, the membranebeing folded into a large number of very closely spaced pleats. Supportmembers are contained in all the pleats on one side of the membrane, allof the edges of which are sealingly embedded in a plastic materialconstituting at least a portion of the housing to give separate fluidchambers on the two sides of the membrane. A first fluid passes throughthe first such chamber within the pleats in a direction generallyparallel to the creases of the pleats while a second fluid flows throughthe second chamber on the opposite side of the membrane pleats in adirection countercurrent to the first fluid. The apparatus isconstructed either by placing the assembled folded membrane in apreconstructed rectangular casing and injecting a plastic material so asto surround and embed the edges of themembrane in the plastic material,or by placing the assembled folded membrane in a mold to form thehousing by injecting a plastic material into the mold so as to surroundand embed the edges of the membrane in the plastic material.

13 Claims, 5 Drawing Figures PATENTEDJAN 2 9 i974 SHEET 1 BF 3IIIIIIIIIIIIIIIIIIIIII CONTRACTUAL ORIGIN OF THE INVENTION Thisinvention was made in the course of, or under, a contract with theUNITED STATES ATOMIC EN- ERGY COMMISSION.

BACKGROUND OF THE INVENTION This invention relates to an apparatus foruse in the dialysis of two fluids and more particularly relates to an Iapparatus for the cleansing of impurities from blood by hemodialysis.

The treatment of patients, numbering well into the thousands throughoutthis country and around the world, who suffer from chronic kidneyfailure, is a serious problem for which no completely satisfactorysolution has yet been found. While kidney transplants may offer apartial solution, transplanting of organs presents other characteristicproblems and is far from a completely satisfactory solution. Thealternative to kidney transplants is the artificial kidney orhemodialyzer. Although hemodialyzers have been used for many years andhave provided successsful treatment for large numbers of kidneypatients, presently available hemodialysis treatment, like kidneytransplantation, does not give a completely satisfactory solution to theproblem of kidney malfunction, and in fact the majority of peoplepresently suffering from kidney malfunction do not receive any suchtreatment. Although there may be many possible reasons for this, twovery predominant reasons are the lack of adequate numbers ofhemodialyzer units and facilities for the vast number of people in needof treatment and the prohibitive costs of such treatment. Although thepresently available and used hemodialyzers have proven successful forthose who have obtained treatment with the units, the number availableis drastically limited in relation to the numbers needed and, inaddition, these hemodialyzers are expensive not only in the initialinvestment in the unit itself but in the costs of continuinghemodialysis treatment as well. Hemodialysis treatment is generallyreceived in a hospital with appropriate facilities on an out-patientbasis, the patient visiting the hospital two or three times a week fortreatment. Treatment is given in the presence of trained medicalpersonnel and a blood transfusion is often required to replace bloodlost to the blood priming volume of the hemodialyzer unit. Although theexpense of continuing treatment can be greatly reduced by having thepatient or his family conduct the treatment in the home, presentlyavailable hemodialyzers and the associated equipment and safety circuitsare very complicated and quite sophisticated so that the majority ofkidney patients and their families are not capable of learning how tooperate such com.- plex equipment. Of the two most commonly usedhemodialyzers, the Kiil dialyzer and the Kolff coil dialyzer, the Kolffcoil dialyzer requires a blood pump and associated machinery, while theKiil dialyzer, although eliminating the need ofa blood pump, requiresrebuilding of the unit under sterile conditions following eachtreatment. In either case, each treatment takes six to fourteen hoursand is given two or three times a week. Unfortunately, in the periodbetween treatments, poisons build up in the patients blood so that bythe end of the three to four day interim period the patient is apt to bequite ill. When the patient does receive treatment, these poisons areremoved from the blood very rapidly so that an imbalance between theblood and the body cells is created which may be so great that the bodychemistry is thrown out of balance and the patient becomes physicallysick during treatment.

Hemodialyzers are presently being developed which will help solve someof these problems. Hemodialyzers such as those coinvented by the presentinventor and forming the subject matter of U. S. Pat. No. 3,522,885 andU. S. Pat. No. 3,565,258 are sufficiently small that they can beoperated without the need of an external blood pump. They are alsoconstructed of inexpensive materials so that not only can they beproduced relatively inexpensively and in large numbers, but they aredisposable, each hemodialyzer unit being discarded after use. However,these hemodialyzers do not offer solutions to many of the presentproblems and, in addition to offering only partially satisfactorysolutions to others, have some drawbacks of their own, such as requiringtubular regenerated cellulose for construction.

Hemodialyzers have also been designed which do not require tubularmembranes, but instead use a sheet of semipermeable membrane. Themajority of these hemodialyzers have rigid frames surrounding theeffective dialysis surface area and support members which haveelaborately designed connected channels for fluid flow. Generally thesesupport members must align exactly to properly form the fluid channels.Such a hemodialyzer is subject of U. S. Pat. No. 3,396,849. Ahemodialyzer which is described in U. S. Pat. No. 3,442,388, issued toDavid B. Pall, has eliminated the need for elaborately designed supportmember-s. This dialyzer has a membrane which has been folded into amultiple number of corrugations adhesively sealed between the two halvesof a plastic housing and provides for passing the two fluids through theunit along the length of the corrugations on opposite sides of themembrane. The support member lies on one side of the membrane and follows the shape of the corrugated membrane. A leaktight adhesive seal iseffected between the housing and the membrane along the entire length ofall the edges of the membrane. Since two of the edges of the membraneundulate back and forth forming the corrugations, they cannot be merelyclamped between two straight edges of the housing halves as is done withthe remaining two straight edges of the membrane, but instead anadhesive material is deposited between the ends of the housing and theundulating edges of the membrane along their entire length to form thisleaktight adhesive seal. Since the adhesive material necessarily willcome into contact with the patients blood, the adhesive must be inertwith respect to the blood, neither reacting with any components in theblood nor releasing any poisons to the blood. Therefore, in selecting anappropriate adhesive for use in this dialyzer, not only mustconsideration be given to the nature of the material forming the housingand the membrane so that the adhesive bonds them together, but theadhesive must be inert with respect to the blood and must not react withthe other materials to produce any substance which is not inert. Whilepresent hemodialyzers use regenerated cellulose for the semipermeablemembrane and acceptable adhesives are known for use with the commonhousing materials, research is being conducted to develop other dialysismembrane materials which will be more efficient than regeneratedcellulose.

Since presently used adhesives may not be acceptable for use with thesenew membranes, new acceptable adhesives would also have to be found foreach new membrane.

The dialyzer of the present invention eliminates the problem of findingan acceptable adhesive for each new type of dialysis membrane materialwhich may be developed as it is easily able to incorporate any dialysismembrane material and also eliminates the difficult problem ofadhesively sealing the edges of the membrane along their entire length.The dialyzer of the present invention can be easily constructed fromrela tively inexpensive materials and is of a design which is readilyadaptable to mechanized production methods. It is intended that adialyzer according to the present invention be used frequently for shortperiods of time and that the unit be discarded after use. The design issufficiently small that it is intended to eliminate the need of a bloodpump and is sufficiently simple to do away with much of the complexassociated equipment and safety circuits. The dialyzer of the presentinvention is designed to be used by the patient in his home under aprogram of daily dialysis for a period of one to two hours. Such a dailydialysis program will eliminate the large buildup of poisons in theblood so that the patient will not only feel better while undergoingtreatment as well as be more alert and hence able to conduct thetreatment himself, but the more frequent removal of poisons from theblood and the shorter lengths of time undergoing treatment will enablethe patient to lead a more normal life.

SUMMARY OF THE INVENTION In accordance with the present invention, adialyzer is provided which employs a semipermeable membrane in sheetform but does not require an adhesive material to effect an adhesiveseal between the membrane and the housing. Instead, the edges of themembrane are sealingly embedded in a plastic material which constitutesat least a portion of the housing. The semipermeable membrane is foldedinto a large number of very closely spaced pleats, support members beinginserted into all those pleats on one side of the membrane while nosupports are placed in the pleats on the opposite side of the membrane.The membrane assemblage is disposed within the housing so that themembrane undulates back and forth across the width of the housing. Oneembodiment employs a preconstructed casing with the two side walls ofthe casing fitting snugly against the pleats in the assemblage and eachof the two side walls being provided at each end with access ports tothe interior of the housing. A plastic material within thepreconstructed casing constitutes a portion of the housing and surroundsthe edges of the membrane sealingly embedding these edges so as to forma separate fluid chamber on each side of the membrane. Alternatively, nopreconstructed casing is used but instead a housing is formed in placeabout the membrane assemblage. The housing is formed by surrounding themembrane assemblage with a plastic material which constitutes the entirehousing and which also surrounds the edges of the membrane and sealinglyembeds these edges so as to form separate fluid chambers on each side ofthe membrane which undulates back and forth across the width of thehousing. Access ports are sealingly mounted on the housing over openingsto the interior of the housing which were created by the removal ofstuds which were appropriately positioned against the membraneassemblage as it was surrounded by the plastic material. In eachembodiment, the access ports provide means for passing one fluid throughone of the separate fluid chambers in a direction generally parallel tothe creases of the pleats and a second fluid through the other fluidchamber on the opposite side of the membrane countercurrent to the firstfluid.

BRIEF DESCRIPTION OF THE DRAWINGS A better understanding of the featuresof the present invention and the inherent advantages can be obtainedfrom a reading of the following description of the invention andreference to the drawings, in which:

FIG. 1 is an isometric view of a dialyzer constructed in accordance withthe present invention which is partially broken away to expose theinterior structure of the dialyzer.

FIG. 2 is a sectional view taken along the line 22 of FIG. 1.

FIG. 3 is a transverse sectional view taken along the line 33 of FIG. 2.

FIG. 4 is a greatly enlarged view of a portion of FIG. 2 to show thedetailed structure of the unit more clearly.

FIG. 5 is a sectional view of an alternative construction.

DESCRIPTION OF THE INVENTION The construction and operation of thepresent invention can be best understood by referring first to FIG. 1wherein there is shown a dialyzer unit in accordance with the presentinvention with one corner broken away to expose the interior structure.There is shown a rectangular housing indicated generally at 1 which hason one side thereof near one end a blood inlet port 2 and on the sameside near the opposite end thereof a blood outlet port 3. Therectangular housing 1 also has on the opposite side thereof a dialysateinlet port 4 located near the same end as the blood outlet port 3 and adialysate outlet port 5 located near the opposite end at the same end ofthe housing 1 as blood inlet port 2. A semipermeable membrane 6 isdisposed within the housing 1. Referring to FIG. 2 and FIG. 3, membrane6 is folded into a very large number of very closely spaced pleats whichextend along the length of the housing and, as is most clearly seen inFIG. 2, undulates back and forth across the width of the housing 1.Support members 7 are disposed within all those pleats which are on oneside of the membrane 6, while those pleats on the opposite side ofmembrane 6 do not contain support members, the support members 7 beingdisposed in those pleats on the side of the membrane 6 whichcommunicates with the dialysate inlet port 4 and dialysate outlet port5. For sake of clarity in the drawings, these support members 7 have notbeen included in FIG. 3. While it is permissible to have support membersin all pleats on both sides of the membrane, it is preferred that therebe support members on only one side. The support members 7 serve to holdthe interior walls of the supported pleats apart, thereby retaining thesupported pleats open for dialysate flow. While other types of supportmembers can be used, it has been found that a nonwoven plastic meshsupport is particularly useful and is preferred. The interior walls ofthe unsupported pleats, those pleats not containing support members, areessentially in contact over the ing under a fluid pressure so that whenblood is introduced into the dialyzer through blood inlet port 2, itwill flow into the unsupported pleats and open them to permit blood flowtherein. The blood flowing within the dialyzer is maintained at apressure slightly greater than the pressure of the dialysate in order todrive water from the blood to the dialysate across the membrane, as itis a normal kidney function to remove excess water from the blood, andthis greater pressure of the blood causes the separation of the normallyclosed unsupported pleats, thereby opening passages for the blood flow.The manner in which this is accomplished can be more easily understoodby turning to FIG. 4 where a portion of the dialyzer has been greatlyenlarged to show the relation of the membrane 6 and the support members7 when the fluids are introduced into the dialyzer. Since the blood isat this slightly higher pressure, the membrane 6 distends into thespaces in the mesh supports 7, thereby opening the closed unsupportedpleats and providing passages for blood flow through the dialyzer. Thetwo interior walls, upper wall 8 and lower wall 9, of normally closedpleat are generally in contact over the larger part of their surfaces.When blood is introduced, however, the membrane 6 distends into thesupport members 7, upper interior wall 8 distending upward toward thesupport member 7 on the opposite side of the membrane 6 above pleat 10,while the lower interior wall 9 distends downward toward the supportmember 7 beneath the pleat ll), this separation of the interior walls 8and 9 opening pleat 10 for blood flow. Fluid flow through the dialyzercan be understood by referring to FIG. 1 and FIG. 3 wherein blood flowis represented by solid arrows and dialysate flow is represented bybroken arrows. Blood enters the dialyzer through blood inlet port 2 anddistributes across the width of the unsupported pleats opening them forflow as above described. The blood then flows within the unsupportedpleats in a direction generally parallel to the creases of the pleatsalong the length of housing 1 toward the opposite end where it exitsfrom the dialyzer through blood outlet port 3. Dialysate enters thedialyzer through dialysate inlet port 4 and distributes across the widthof the supported pleats. Dialysate flows within the supported pleats onthe opposite side of membrane 6 from the blood in a direction generallyparallel to the creases and countercurrent to the blood flow. Dialysateflows along the length of the housing 1 toward dialysate outlet port 5through which it exits from the dialyzer.

In one embodiment of the present invention, which embodiment isillustrated in FIGS. 2 4, the housing 1 comprises an outer portion laand an inner portion lb. Outer portion 1a is a preconstructedrectangular casing having on the, opposite ends of each of the two sidewalls thereof a fluid inlet port and a fluid outlet port which provideaccess to the interior of the housing 1. Inner portion 1b consists of aplastic material 11 which surrounds all the edges of the membrane 6sealingly embedding these edges so as to form separate fluid chambers onthe opposite sides of membrane 6. One of these chambers is for dialysateflow and consists of the interiors of the supported pleats while theother chamber is for blood flow and consists of the interiors of theunsupported pleats. Flow through these chambers is as described above.The side-edges l2 and 13 of membrane 6, side-edges 12 and 13 being thoseedges of the membrane 6 which are perpendicular to the creases of thepleats and which undulate back and forth across the width of the housing1, are surrounded by and sealingly embedded in plastic material 11 nearthe ends of housing 1, as is best seen in FIG, 3. Plastic material 11extends a slight distance into the supported pleats so as to surroundside-edges 12 and 13 and extends to the ends of the casing lla so as toconstitute a portion of the walls of housing 1. The end-edges 14 and 15of membrane 6, end-edges l4 and 15 being those edges of the membrane 6which are parallel to the creases of the pleats and which extend alongthe length of housing 1, are likewise surrounded by and sealinglyembedded in plastic material 11 near the top and bottom of housing ll.As is apparent in FIG. 3, end-edges 14 and 15 are completely surroundedby plastic material 11 along their entire length along the top andbottom of housing 1. Referring to FIG. 2, it is seen that end-edge 14forms one part of first pleat 16 while end-edge 15 forms one part oflast pleat 17. First pleat l6 and last pleat 17 are filled with plasticmaterial 11, thereby completely surrounding and embedding end-edges 14and 15, plastic material 11 extending to the top and bottom of theeasing lla so as to again constitute a portion of housing 1. Since allthe edges of membrane 6 are sealingly embedded in the plastic material11, the chambers on the two sides of membrane 6 are separated from eachother and intermingling of blood and dialysate is prevented.

In a preferred embodiment of the present invention, the flrst pleast 16and the last pleat 17 open to the same side of housing 1 and are amongthose pleats which contain support members. These support membersdisposed in first pleat 16 and last pleat 17 can be considered asspacing members as they serve to hold pleats 16 and 17 open to permitplastic material 11 to fill these pleats, thereby surrouding end-edges14 and 15. To further facilitate the introduction of plastic material 11into the first and last pleats 16 and 17, these pleats ex tend onlypartway across the'width of the housing, endedge 14 and end-edge 15which form a portion of first pleat 16 and last pleat 17, respectively,terminating at a line approximately one-half the distance across thewidth of the housing, as is depicted in FIG. 2. The plastic material 11can then be readily introduced into pleats l6 and 17 around end-edges 14and 15 which are near the midpoints of the top and bottom of the housing1.

Referring to FIG. 2 and the embodiment in which a preconstructedrectangular casing 1a is used, it can be seen that the two side walls 21and 22 of the casing 1a fit snugly against the undulating membrane 6.Since there is this snug fit between the membrane 6 and the side walls21 and 22, plastic material 11 does not extend along the interior of theside walls. In an alternative embodiment of the present invention, whichembodiment is illustrated in FIG. 5, plastic material 11 forms theentire housing 1 rather than constituting only a portion of it, nopreconstructed casing being used. Consequently, in the alternativeembodiment, a first barrier sheet 18 and a second barrier sheet 19overlap and cover the openings to the supported pleats which face theside of the housing, these barrier sheets preventing plastic material11, which surrounds and sealingly embeds all the edges of membrane 6 asdescribed above, from filling any of that portion of the openedsupported pleats. Barrier sheets 18 and 19 essentially lie between thesupported pleats and the interior side wall of housing 1 and lie alongthe length of the housing 1 between dialysate inlet 4 and dialysateoutlet 5. First barrier sheet 18 has one edge extending into the firstpleat 16 between the contained support member 7 and the lower interiorwall of pleat 16 which also forms a portion of the adjacent pleat, andextends across the membrane pleats towards the last pleat 17. Secondbarrier sheet 19 has one edge extending into the last pleat 17 betweenthe contained support member 7 and the upper interior wall of pleat 17which also forms a portion of the adjacent pleat, and extends across themembrane pleats towards the first pleat l6, overlapping with barriersheet 18. While these barrier sheets can be chosen from a wide varietyof materials, thin sheets of polycarbonate and polypropylene have beenfound to be very satisfactory.

The use of barrier sheets on the dialysate side of the membrane pleatsin the alternative embodiment is dictated by the method of making theparticular embodiment. In constructing either embodiment of the presentinvention, the semipermeable dialysis membrane is folded into a largenumber of very closely spaced pleats of the desired width. In thepreferred embodiments, the membrane is folded into an odd number ofpleats so that the first and last pleat open to the same side ofthemembrane and is further folded such that the endedges of the membraneterminate at a line approximately one-half the distance across the widthof the other pleats. Support members, preferably plastic nonwoven meshsupports, are inserted into all pleats on one side of the membrane, thisbeing the same side of the membrane as the first and last pleats in thepreferred embodiment. Spacing members are inserted into both the firstpleat and the last pleat to maintain these pleats substantially opened,the support member serving as the spacing member in the preferredembodiment. The spacing members can be of any shape or structure whichwill maintain space between two abutting surfaces while permitting afluid plastic material to flow around and through the member. Theabovedescribed nonwoven mesh support members serve well as spacingmembers. Other spacing members are placed on the outside of the firstand last pleat so as to encompass the two end-edges of the membranebetween spacing members. If barrier sheets are to be used, they areinserted into the first and last pleats between the contained supportmember and the adjacent pleat of the membrane and extend over theopenings in the supported pleats so as to overlap and cover theseopenings. They further extend along the length of the pleats between theopenings to the interior of the pleats associated with the inlet andoutlet ports. When a we constructed rectangular plastic casing is used,these barrier sheets are not essential, although they can still be usedwith no ill effects. lnstead, the above membrane assemblage, comprisingthe folded membrane, the support members, the spacing members andoptionally the barrier s'heets, is placed in the rectangular casing sothat the two end-edges of the membrane are adjacent the top and bottomof the casing, the membrane consequently undulating across its width.The casing is of such dimensions that the top, bottom, and two sidewalls fit snugly against the membrane assemblage, the side walls fittingvery snugly so as to function similarly to the barrier sheets inpreventing flow of plastic material into the supported pleats, while anarrow gap is left between the side-edges of the membrane which form theends of the assemblage and the ends of the casing. Both of the sidewalls of the casing have an inlet port at one end and an outlet portnear the opposite end, these ports being of identical structure andlabeled inlet or outlet only for sake of convenience. A fluid plasticmaterial is injected into the casing through the top, bottom, and eachof the two ends of the casing. The plastic material flows along the topand bottom walls of the casing around and through the spacing membersand around the end-edges of the membrane to fill the first and lastpleats, thereby completely surrounding the end-edges of the membrane.The plastic material can more readily flow around the end-edges of themembrane to fill the first and last pleats when the end-edges terminateone-half the distance across the width of the casing as in the preferredembodiment. The fluid plastic material also fills the narrow spacebetween the side-edges of the membrane and the end walls of the casingand flows a short distance into the supported pleats which are slightlyopened by the support members. The two side-edges of the membrane arethereby surrounded by the plastic material as well as the two end-edges.The viscosity of the fluid plastic material is adjusted so as to controlits flow characteristics, it being desirable to have it sufficientlythin to flow so as to surround the edges of the membrane butsufficiently viscous that it can flow only a short distance into thepleats, as flow into the pleats would reduce the membrane area availablefor dialysis. The plastic material does not flow into the unsupportedpleats as their interior walls are essentially in contact over theirentire surface until a fluid is introduced, the unsupported pleats beingessentially closed. The viscosity of the plastic material is also suchthat the snug fit between the side walls of the casing and the membraneassemblage prevents flow along the side walls. The fluid plasticmaterial is subsequently solidified whereby, having filled the I spacealong the interior walls of the casing, it constitutes a portion of thehousing. The edges of the membrane are thereby sealingly embedded in theplastic material, thereby dividing the dialyzer into two separatechambers on the two opposite sides of the membrane. Since the edges areembedded, an adhesive seal between the plastic material and the membraneis not necessary, and although the plastic material can be an adhesiveit need not be one but can be chosen from a wide variety of materialsinert to the blood which can be injected as a plastic capable of flowingand subsequently solidified. The plastic material must remain solid atroom temperature and slightly above after solidifying, thesolidification being effected in any of a variety of ways dependent uponthe material, such as cooling below a melting point, heat curing,chemical curing, etc. Examples of substances which can be used as theplastic material are polyethylene, polypropylene, polycarbonate, epoxyresins, polyester resins, polystyrene, etc.

A particular example of a plastic material formulation which has beenused successfully is parts of EPON 828, a diglycidal ether of bisphenylA epoxy resin produced by Shell Chemical Company, parts oftriethylenetetraamine which acts as a curing agent, and 10-12 parts of athickening agent Cab-O-Sil which is a silica aerogel produced by CabotCorporation. While the above formulation has good adhesivecharacteristics, it is not necessary thatthe plastic material be a goodadhesive and in fact another formulation which has poor adhesivecharacteristics but has also been used successfully is 100 parts of EPON828, 24 parts of Cab-O-Sil, and 100 parts of Versamid 140 which is thereaction product of an excess of a polyfunctional amine and apoly-functional fatty acid and is produced by General Mills.

An alternative method of making the dialyzer of the present invention.does not incorporate a preconstructed rectangular casing but insteadthe housing is formed about the membrane assemblage. The abovedescribedmembrane assemblage is placed into a rectangular mold rather than apreconstructed casing and the housing is formed about the membraneassemblage within the mold. The mold is of such dimensions that thespacing members surrounding the membrane are held between the top andbottom of the mold while a narrow gap is left between the membraneassemblage and the side and end walls of the mold. Studs, eitherintegral with the mold or placed therein, occupy the narrow gap betweenthe membrane assemblage and the side wall of the mold near each end ofeach side wall. These studs extend vertically from the first pleat tothe last pleat and fit snugly against the membrane assemblage so as toprevent plastic material from sealing off the entire side of themembrane assemblage, the openings left by the studs serving as accessports to the dialyzer interior. The plastic material is then injectedinto the mold and solidified. The plastic material surrounds andsealingly embeds all edges of the membrane as described above and alsofills the gaps on the sides and ends of the mold and within the spacingmembers to form the plastic housing about the embedded membrane. Thebarrier sheets, if. used, prevent any plastic material from entering theopened pleats which may happen to' a small degree if no barrier sheetsare used. After the housing is removed from the mold, thestuds areremoved, exposing openings to the two interior chambers on the two sidesof the membrane. Inlet and outlet ports are sealingly mounted on thehousing over these openings to complete construction of the dialyzer.Alternatively, inlet and outlet ports can be placed in the mold in placeof the studs and molded into place or the ports can be formed in themold with the housing by an appropriately constructed mold.

In the embodiments of the present invention and by each of the disclosedmethods of making the dialyzer, the edges of the membrane are surroundedby and sealingly embedded in a plastic material which constitutes aportion of or forms the entire housing. Since the edges are sealinglyembedded, the need of an adhesive material to effect an adhesive bondbetween the membrane and the housing has been eliminated. This permits awider variety of dialysis membranes to be used and new dialysismembranes can be employed without the need of developing or finding anew compatible adhesiveboncling agent. The use of sheet form rather thantubular form membrane increases the potential use of the design, as manydialysis membrane materials cannot be made in tubular form, as well aslowers the cost of construction, as sheet membrane is generally lessexpensive than tubular forms. The costs of construction of the dialyzerof the present invention are relatively low, since inexpensive materialscan be used and the methods of construction are adaptable to moremechanized techniques. The dialyzer is sufficiently small that a bloodpump is not necessary, and it is intended to produce the disposabledialyzers at a sufficiently low cost and in sufficient numbers to permitdaily dialysis for short times in the home without the presence oftrained medical personnel.

While the present invention has been described as a hemodialyzer withfrequent references to dialysate fluid and blood, the invention is notso limited but is equally adaptable to other forms of dialysis and hasbeen described as a hemodialyzer solely for sake of convenience. It willbe understood that the invention is not limited to the details givenherein but that it may be modified within the scope of the appendedclaims.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:

1. A dialyzer comprising: a rectangular housing; a semipermeablemembrane disposed within said housing, said membrane being folded into alarge number of very closely spaced pleats so as to undulate across thewidth of said housing, all edges of said membrane being embedded in anonadhesive plastic material selected from the group consisting ofpolycarbonate, polypropylene, polyethylene, and polystyrene, saidnonadhesiveplastic material constituting at least a portion of saidhousing to form thereby a first fluid chamber on one side of saidmembrane sealingly separated from a second fluid chamber on the oppositeside of said membrane; support members disposed within all pleats on oneside only of said membrane; means for passing a first fluid through saidfirst chamber in a direction generally parallel to the creases of saidpleats; and means for passing a second fluid through said second chambercountercurrent to the first fluid.

2. A dialyzer in accordance with claim 1 wherein:.

said plastic material fills the space along the interior walls of apreconstructed rectangular casing so as to constitute a portion of saidhousing and so as to surround the edges of said membrane.

3. The dialyzer according to claim 2 wherein the first pleat and thelast pleat in'said semipermeable membrane open to the same side of saidhousing and the support members are disposed in said first pleat, saidlast pleat, and all other pleats on the same side of said membrane. g

4. The dialyzer according to claim 3 wherein the first pleat and thelast pleat in said membrane extend only part way across the width ofsaid housing, the endedges of said membrane terminating at a lineapproxi mately one-half of the distance across the width of the housing,said plastic material filling said first pleat and said last pleat so asto completely surround said endedges of said membrane.

5. A dialyzer in accordance with claim 2 wherein the semipermeablemembrane is folded such that those pleats not containing support memberstherein are essentially closed in the absence of a fluid, the portionsof the membrane surface forming the opposite interior walls of each ofthese pleats being essentially in contact, and opened in the presence ofa fluid, these pleats being capable of opening under a fluid pressurewhich distends the membrane into the support members in the pleats onthe opposite side of said membrane.

6. A dialyzer in accordance with claim 1 wherein: said plastic materialconstitutes the entire housing, surrounding the edges of the membraneand completely enclosing the entire undulating membrane so as to form arectangular housing.

7. A dialyzer in accordance with claim 6 wherein the semipermeablemembrane is folded such that those pleats not containing support memberstherein are essentially closed in the absence of a fluid, the portionsof the membrane surface forming the opposite interior walls of each ofthese pleats being essentially in contact, and opened in the presence ofa fluid, these unsupported pleats being capable of opening under a fluidpressure which distends the membrane into the support members disposedin the pleats on the opposite side of said membrane.

8. A dialyzer in accordance with claim 7 wherein the first pleat and thelast pleat in said semipermeable membrane are on the same side of saidmembrane and the support members are disposed in said first and lastpleats and the other pleats on' the same side of the membrane; andwherein said dialyzer further comprises a first barrier sheet and asecond barrier sheet disposed within said housing on the same side ofthe membrane as said support members and essentially lying between saidsupported pleats and the interior side wall of said housing, said firstbarrier sheet having one edge inserted into the first pleat between thecontained support member and the adjacent pleat, said first barriersheet extending over the membrane pleats towards said last pleat, saidsecond barrier sheet having one edge inserted into the last pleatbetween the contained support member and the adjacent pleat, said secondbarrier sheet extending over the membrane pleats towards said firstpleat so as to overlap said first barrier sheet, said two barrier sheetslying along the length of the side of the housing so as to cover theopenings in the supported pleats parallel to the creases of the pleatsand to prevent the plastic material from extending into said supportedpleats.

9. A dialyzer according to claim 8 wherein the first pleat and the lastpleat in said membrane extend only part way across the width of saidhousing, the endedges of said membrane terminating at a lineapproximately one-half of the distance across the width of the housing,said plastic material filling said first pleat and said last pleat so asto completely surround said endedges of said membrane.

10. A method of making the dialyzer of claim 2 comprising:

a. folding a semipermeable membrane into a large number of very closelyspaced pleats;

b. inserting support members into all pleats on one side of saidmembrane; 7

c. inserting spacing members into both the first pleat and the lastpleat to maintain said first and last pleats substantially opened;

d. placing spacing members on the outside of said first pleat and on theoutside of said last pleat whereby each of the two end-edges of saidmembrane lie between spacing members on the outside of the pleat and aspacing member within the pleat;

e. placing the above membrane assemblage into a rectangular casing, saidrectangular casing having on each of the two side walls thereof an inletport near one end and an outlet port near the opposite end, saidmembrane assemblage being placed such that the two end-edges of themembrane and their associated spacing members are adjacent the top andbottom walls of said casing and said membrane assemblage fits snuglyagainst the top, bottom, and two side walls of said casing while anarrow space is left between the side-edges of the membrane which formthe ends of the assemblage and the end walls of the casing;

f. injecting into said casing through the top, bottom,

and each of the two end walls, a fluid plastic material which flowsalong said top and bottom walls and fills said substantially openedfirst and last pleats, thereby completely surrounding said two end-edgesof the membrane, and which fills said narrow spaces between saidside-edges of the membrane and the end walls of the casing and whichflows a short distance into the supported pleats which are held slightlyopened by said support members, thereby surrounding said two side-edgesof the membrane; and

g. solidifying said fluid plastic material whereby all edges of saidmembrane are embedded in said plastic material which forms a portion ofthe housing and said housing is divided into two sealingly separatefluid chambers on opposite sides of said membrane.

11. A method of making the dialyzer of claim 6 comprising:

a. folding the semipermeable membrane into a large number of veryclosely spaced pleats;

b. inserting support members into all pleats on one side of saidmembrane;

c. inserting spacing members into both the first pleat and the lastpleat to maintain said first and last pleats substantially opened;

d. placing spacing members on the outside of said first pleat and on theoutside of said last pleat whereby each of the two end-edges of saidmembrane lie between spacing members on the outside of the pleat and aspacing member within the pleat;

e. placing the above membrane assemblage into a rectangular mold of suchinternal dimensions that the support members about the end-edges of themembrane contact the top and bottom walls of said mold while a narrowgap is left between the membrane assemblage and the two side walls ofthe mold and between the side-edges of the membrane which form the endsof the assemblage and the two end walls of the mold;

. placing studs in the narrow gap between said membrane assemblage andsaid mold near each end of each side wall thereof, said studs extendingvertically from the first pleat to the last pleat and fitting snuglybetween the side walls of said mold and said membrane assemblage;

g. injecting into said mold a fluid plastic material, said fluid plasticmaterial flowing into and filling said narrow gap between said membraneassemblage and said side walls of said mold between and about saidstuds, flowing into and filling said narrow gap between the side-edgesof the membrane which form the ends of the assemblage and the end wallsof said mold and further flowing form this gap a short distance into thesupported pleats which are held slightly opened by said support membersthereby surrounding said two side-edges of the membrane, and flowinginto and about said spacing members and into and filling saidsubstantially opened first and last pleats thereby completelysurrounding said two end-edges of said membrane; h. solidifying saidfluid plastic material whereby all edges of said membrane are embeddedin said plastic material and said plastic material forms a hous ingabout said membrane assemblage, said housing having openings to itsinterior at the points of mold, placing a first and a second barriersheet along the side of said membrane assemblage on the same side ofsaid membrane as said support members, one edge of said first barriersheet being inserted between the support member and a membrane wall ofthe first supported pleat, said first barrier sheet extending over thepleats towards the last pleat, one edge of said second barrier sheetbeing inserted between the support member and a membrane wall of thelast supported pleat, said second barrier sheet extending over thepleats toward the first pleat so as to overlap with said first barriersheet, said first and second barrier sheets being of such a length so asto extend along the length of the side of the assemblage between saidstuds.

13. A method according to claim 12 wherein said membrane is folded suchthat the first pleat and the last pleat extend only part way across thewidth of the other pleats, the end-edges of said membrane terminating ata line approximately one-half the distance across the width of thepleats, and the first and last pleats are on the same side ofthemembrane and have support members inserted therein.

1. A dialyzer comprising: a rectangular housing; a semipermeablemembrane disposed within said housing, said membrane being folded into alarge number of very closely spaced pleats so as to undulate across thewidth of said housing, all edges of said membrane being embedded in anonadhesive plastic material selected from the group consisting ofpolycarbonate, polypropylene, polyethylene, and polystyrene, saidnonadhesive plastic material constituting at least a portion of saidhousing to form thereby a first fluid chamber on one side of saidmembrane sealingly separated from a second fluid chamber on the oppositeside of said membrane; support members disposed within all pleats on oneside only of said membrane; means for passing a first fluid through saidfirst chamber in a direction generally parallel to the creases of saidpleats; and means for passing a second fluid through said second chambercountercurrent to the first fluid.
 2. A dialyzer in accordance withclaim 1 wherein: said plastic material fills the space along theinterior walls of a preconstructed rectangular casing so as toconstitute a portion of said housing and so as to surround the edges ofsaid membrane.
 3. The dialyzer according to claim 2 wherein the firstpleat and the last pleat in said semipermeable membrane open to the sameside of said housing and the support members are disposed in said firstpleat, said last pleat, and all other pleats on the same side of saidmembrane.
 4. The dialyzer according to claim 3 wherein the first pleatand the last pleat in said membrane extend only part way across thewidth of said houSing, the end-edges of said membrane terminating at aline approximately one-half of the distance across the width of thehousing, said plastic material filling said first pleat and said lastpleat so as to completely surround said end-edges of said membrane.
 5. Adialyzer in accordance with claim 2 wherein the semipermeable membraneis folded such that those pleats not containing support members thereinare essentially closed in the absence of a fluid, the portions of themembrane surface forming the opposite interior walls of each of thesepleats being essentially in contact, and opened in the presence of afluid, these pleats being capable of opening under a fluid pressurewhich distends the membrane into the support members in the pleats onthe opposite side of said membrane.
 6. A dialyzer in accordance withclaim 1 wherein: said plastic material constitutes the entire housing,surrounding the edges of the membrane and completely enclosing theentire undulating membrane so as to form a rectangular housing.
 7. Adialyzer in accordance with claim 6 wherein the semipermeable membraneis folded such that those pleats not containing support members thereinare essentially closed in the absence of a fluid, the portions of themembrane surface forming the opposite interior walls of each of thesepleats being essentially in contact, and opened in the presence of afluid, these unsupported pleats being capable of opening under a fluidpressure which distends the membrane into the support members disposedin the pleats on the opposite side of said membrane.
 8. A dialyzer inaccordance with claim 7 wherein the first pleat and the last pleat insaid semipermeable membrane are on the same side of said membrane andthe support members are disposed in said first and last pleats and theother pleats on the same side of the membrane; and wherein said dialyzerfurther comprises a first barrier sheet and a second barrier sheetdisposed within said housing on the same side of the membrane as saidsupport members and essentially lying between said supported pleats andthe interior side wall of said housing, said first barrier sheet havingone edge inserted into the first pleat between the contained supportmember and the adjacent pleat, said first barrier sheet extending overthe membrane pleats towards said last pleat, said second barrier sheethaving one edge inserted into the last pleat between the containedsupport member and the adjacent pleat, said second barrier sheetextending over the membrane pleats towards said first pleat so as tooverlap said first barrier sheet, said two barrier sheets lying alongthe length of the side of the housing so as to cover the openings in thesupported pleats parallel to the creases of the pleats and to preventthe plastic material from extending into said supported pleats.
 9. Adialyzer according to claim 8 wherein the first pleat and the last pleatin said membrane extend only part way across the width of said housing,the end-edges of said membrane terminating at a line approximatelyone-half of the distance across the width of the housing, said plasticmaterial filling said first pleat and said last pleat so as tocompletely surround said end-edges of said membrane.
 10. A method ofmaking the dialyzer of claim 2 comprising: a. folding a semipermeablemembrane into a large number of very closely spaced pleats; b. insertingsupport members into all pleats on one side of said membrane; c.inserting spacing members into both the first pleat and the last pleatto maintain said first and last pleats substantially opened; d. placingspacing members on the outside of said first pleat and on the outside ofsaid last pleat whereby each of the two end-edges of said membrane liebetween spacing members on the outside of the pleat and a spacing memberwithin the pleat; e. placing the above membrane assemblage into arectangular casing, said rectangular casing having on each of the twoside walls thereof an inlet port Near one end and an outlet port nearthe opposite end, said membrane assemblage being placed such that thetwo end-edges of the membrane and their associated spacing members areadjacent the top and bottom walls of said casing and said membraneassemblage fits snugly against the top, bottom, and two side walls ofsaid casing while a narrow space is left between the side-edges of themembrane which form the ends of the assemblage and the end walls of thecasing; f. injecting into said casing through the top, bottom, and eachof the two end walls, a fluid plastic material which flows along saidtop and bottom walls and fills said substantially opened first and lastpleats, thereby completely surrounding said two end-edges of themembrane, and which fills said narrow spaces between said side-edges ofthe membrane and the end walls of the casing and which flows a shortdistance into the supported pleats which are held slightly opened bysaid support members, thereby surrounding said two side-edges of themembrane; and g. solidifying said fluid plastic material whereby alledges of said membrane are embedded in said plastic material which formsa portion of the housing and said housing is divided into two sealinglyseparate fluid chambers on opposite sides of said membrane.
 11. A methodof making the dialyzer of claim 6 comprising: a. folding thesemipermeable membrane into a large number of very closely spacedpleats; b. inserting support members into all pleats on one side of saidmembrane; c. inserting spacing members into both the first pleat and thelast pleat to maintain said first and last pleats substantially opened;d. placing spacing members on the outside of said first pleat and on theoutside of said last pleat whereby each of the two end-edges of saidmembrane lie between spacing members on the outside of the pleat and aspacing member within the pleat; e. placing the above membraneassemblage into a rectangular mold of such internal dimensions that thesupport members about the end-edges of the membrane contact the top andbottom walls of said mold while a narrow gap is left between themembrane assemblage and the two side walls of the mold and between theside-edges of the membrane which form the ends of the assemblage and thetwo end walls of the mold; f. placing studs in the narrow gap betweensaid membrane assemblage and said mold near each end of each side wallthereof, said studs extending vertically from the first pleat to thelast pleat and fitting snugly between the side walls of said mold andsaid membrane assemblage; g. injecting into said mold a fluid plasticmaterial, said fluid plastic material flowing into and filling saidnarrow gap between said membrane assemblage and said side walls of saidmold between and about said studs, flowing into and filling said narrowgap between the side-edges of the membrane which form the ends of theassemblage and the end walls of said mold and further flowing form thisgap a short distance into the supported pleats which are held slightlyopened by said support members thereby surrounding said two side-edgesof the membrane, and flowing into and about said spacing members andinto and filling said substantially opened first and last pleats therebycompletely surrounding said two end-edges of said membrane; h.solidifying said fluid plastic material whereby all edges of saidmembrane are embedded in said plastic material and said plastic materialforms a housing about said membrane assemblage, said housing havingopenings to its interior at the points of contact between said membraneassemblage and said studs; i. removing said housing from said mold; j.removing said studs from said housing to expose said openings to theinterior; and k. sealingly mounting access ports on said housing oversaid openings.
 12. A method according to claim 11 further comprising:prior to placing the membrane assemblage in the mold, placing a firstand a second barrier sheet aLong the side of said membrane assemblage onthe same side of said membrane as said support members, one edge of saidfirst barrier sheet being inserted between the support member and amembrane wall of the first supported pleat, said first barrier sheetextending over the pleats towards the last pleat, one edge of saidsecond barrier sheet being inserted between the support member and amembrane wall of the last supported pleat, said second barrier sheetextending over the pleats toward the first pleat so as to overlap withsaid first barrier sheet, said first and second barrier sheets being ofsuch a length so as to extend along the length of the side of theassemblage between said studs.
 13. A method according to claim 12wherein said membrane is folded such that the first pleat and the lastpleat extend only part way across the width of the other pleats, theend-edges of said membrane terminating at a line approximately one-halfthe distance across the width of the pleats, and the first and lastpleats are on the same side of the membrane and have support membersinserted therein.